Hello Amanda,
Sorry I can't help you with the rim sizes, I guess only the manufacturer can answer that question 100%.
I was thinking about your quest ;-) while riding on a hardened-snow bike path yesterday and a few points came up.
1. Riding on hard-snow paths is usually quite bumpy, some sections can be as uncomfortable as riding on a path of hard-dried mud in the countryside with the bike shaking all over the place.
So best to save some budget for a good suspended seatpost like the Suntour SP12-NCX, good value for money (approx 70$).
(Link Removed - No Longer Exists)
It will replace your factory-version easily, make sure you pickup the right diameter 27.2mm or 31.6mm.
Here's an nice video test where you can see both the road and the seatpost in action:
And again, get wide tires (doesn't have to be fat tires though), at least 42mm wide, 47mm is neat. And run them at lowest pressure allowed for better grip and comfort.
2. You seem to consider some online vendors instead of buying to a major brand from your LBS (Local Bike Shop ?) reseller.
A word of caution: check with your LBS first how cooperative it is with supporting ebikes bought online.
Some can be brutal with customers who bought online ...
Of course, this may be a side-issue if you are used to maintain and tune your bike already.
Acid Test: can you change your chain by yourself (which includes a specific tool) ?
Yes: you are good to fly solo
No: your LBS is your trusted mate
3. Since your commute is so short (5km), do you really need a large battery ?
BH Easy Motion (big brand, lots of resellers, maybe one next to you) has a range of bikes with small batteries fitting right below the seat, the Easy Go.
Easy to remove the battery and fit in your bag/drawer, plus the connection being under the saddle, it's more protected from rain/snow than on a frame.
Here's a review from 2016 Easy Go Street:
https://electricbikereview.com/easy-motion/easygo-street/
But the neat part is that they revamped the serie for the 2017 collection so it should be way cheaper (1199$ vs 1699$) and maybe a larger battery capacity (250Wh vs 210Wh).
Court interviewed them at Interbike a month ago, check the sequence at 5:30min to 8:00 for price and battery position.
HTH
T.